Welding ISO Disc Tabs onto a frame?

Duncan Smith said the following on 16/10/2007 12:20:

Quoted message said:

Say you have a steel frame (like an On One Pompino) and would like to
fit a rear disc - but there's only mounts for canties. Would the LBS
likely be able to weld some ISO tabs on, would it be a good idea, and
what may it cost?

You'd have to think very carefully about where the braking forces are
going to go, and a quick look at a photo shows that there's not much to
take those forces! You ought to think about a brace between the seat
stay and the chain stay.

You might just invalidate any warranty :-)

--
Paul Boyd
http://www.paul-boyd.co.uk/

Duncan Smith said:

Say you have a steel frame (like an On One Pompino) and would like to
fit a rear disc - but there's only mounts for canties. Would the LBS
likely be able to weld some ISO tabs on, would it be a good idea, and
what may it cost?

LBS - no, at least not unless it does framebuilding jobs.

Framebuilder or someone with appropriate equipment; yes.

There is a question as to whether the tubes are strong enough to take the
brake forces, but I suspect the Pompino isn't likely to be so "light weight"
to have such thin tubes to be unable to take the forces.

Cost; two parts
- the fitting of the tabs, shouldn't be more than a few tens of pounds.
- making the paint good. This is the potentially expensive part. If you
just kept the re-paint to the rear-stays and possibly the drop-out and
horizontal stays, they cost isn't likely to be too bad.

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

Nigel Cliffe said:

Duncan Smith said:

Say you have a steel frame (like an On One Pompino) and would like to
fit a rear disc - but there's only mounts for canties. Would the LBS
likely be able to weld some ISO tabs on, would it be a good idea, and
what may it cost?

LBS - no, at least not unless it does framebuilding jobs.

Framebuilder or someone with appropriate equipment; yes.

There is a question as to whether the tubes are strong enough to take the
brake forces, but I suspect the Pompino isn't likely to be so "light weight"
to have such thin tubes to be unable to take the forces.

Cost; two parts
- the fitting of the tabs, shouldn't be more than a few tens of pounds.
- making the paint good. This is the potentially expensive part. If you
just kept the re-paint to the rear-stays and possibly the drop-out and
horizontal stays, they cost isn't likely to be too bad.

Doesn't sound too bad. I think the Pompino will be tuff enough and
voiding the warranty wont matter too much (frame cost is barley into 3
digits).

It's a working bike, so perhaps I could skimp on the paint job - lick
of Hammerite to prevent rust?

I know of Brian Rourkes in Busrlem who may take it on. Any other
recommendations - N'pton, MK, or Stoke area would be ideal, but not
necessary...

Thanks,

Duncan

"Duncan Smith" <[email hidden]> a écrit:

Quoted message said:

Would the LBS likely be able to weld some ISO tabs on, would
it be a good idea, and what may it cost?

Argos charge 40gbp:

http://www.argoscycles.co.uk/renovation-pricelist.htm

and Mercian the same:

http://www.merciancycles.com/renovation.asp

I don't know whether or not that would include any necessary reinforcement
of the stays. Steel disk frames often use a brace between the seatstay and
chainstay.

The situation is complicated by the Pompino's track ends. You'll need to
allow for axle movement in the design of the braze-on, and a standard ISO
mount won't allow any adjustment. One option would be a slotted mount as
used on some of the other On-Ones:

http://www.on-one.co.uk/images/announce/sandrotorside.jpg

http://www.on-one.co.uk/images/announce/slidingdropout.jpg

http://www.on-one.co.uk/images/pagemaster/slotdrop500w.jpg

but it wouldn't be straightforward to fit, and the price will rise
accordingly.

Personally I'd consider a new frame:

http://www.bikemagic.com/news/article.asp?UAN=4849&v=1

or - more probably - leave things as they are.

James Thomson

James Thomson said:

"Duncan Smith" <[email hidden]> a écrit:

Quoted message said:

Would the LBS likely be able to weld some ISO tabs on, would
it be a good idea, and what may it cost?

Argos charge 40gbp:

http://www.argoscycles.co.uk/renovation-pricelist.htm

and Mercian the same:

http://www.merciancycles.com/renovation.asp

I don't know whether or not that would include any necessary reinforcement
of the stays. Steel disk frames often use a brace between the seatstay and
chainstay.

The situation is complicated by the Pompino's track ends. You'll need to
allow for axle movement in the design of the braze-on, and a standard ISO
mount won't allow any adjustment. One option would be a slotted mount as
used on some of the other On-Ones:

http://www.on-one.co.uk/images/announce/sandrotorside.jpg

http://www.on-one.co.uk/images/announce/slidingdropout.jpg

http://www.on-one.co.uk/images/pagemaster/slotdrop500w.jpg

but it wouldn't be straightforward to fit, and the price will rise
accordingly.

Personally I'd consider a new frame:

http://www.bikemagic.com/news/article.asp?UAN=4849&v=1

or - more probably - leave things as they are.

Interesting options, I like the sliding drop-outs on the in-bred and
road rat - expect you're right, I'll just leave things as they are and
run a V-brake in the winter maybe.

Thanks,

Duncan

In news:[email hidden],
Duncan Smith <[email hidden]> tweaked the Babbage-Engine to tell
us:

Quoted message said:

Interesting options, I like the sliding drop-outs on the in-bred and
road rat - expect you're right, I'll just leave things as they are and
run a V-brake in the winter maybe.

Certainly rather simplere than the Ibis Tranny:
http://www.velonews.com/tech/report/articles/13443.0.html

Disclaimer: I have a Roadrat (though it doesn't have a rear brake at all)

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
There's a village in Texas that's missing its idiot.

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Say you have a steel frame (like an On One Pompino) and would like to
fit a rear disc - but there's only mounts for canties. Would the LBS
likely be able to weld some ISO tabs on, would it be a good idea, and
what may it cost?

You can buy bolt on disc brake mounts that basically clamp onto the seat
and chain stays. I'm on a slowish connection at the moment but if no-
one else has come up with a link, I'll have a look later when I am back
on broadband

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

Tony Raven said:

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Say you have a steel frame (like an On One Pompino) and would like to
fit a rear disc - but there's only mounts for canties. Would the LBS
likely be able to weld some ISO tabs on, would it be a good idea, and
what may it cost?

I do wonder if it is worth putting a disc brake on the rear if it needs
frame modification. The rear brake does not have much stopping power,
and canti's will easily lock the wheel.

Quoted message said:

You can buy bolt on disc brake mounts that basically clamp onto the seat
and chain stays. I'm on a slowish connection at the moment but if no-
one else has come up with a link, I'll have a look later when I am back
on broadband

A quick look gives

http://www.bikemag.com/gear/braketherapy/

Quoted message said:

Quoted message said:

You can buy bolt on disc brake mounts that basically clamp onto the seat
and chain stays. I'm on a slowish connection at the moment but if no-
one else has come up with a link, I'll have a look later when I am back
on broadband

A quick look gives

That's pretty interesting, hadn't heard of those before...

Thanks,

Duncan